A JUnit TestWatcher to take screenshot when test fails.

ScreenshotRule.java

package com.ibm.robot.web.testrules;

import java.io.File;
import java.io.IOException;
import org.apache.commons.io.FileUtils;

import org.junit.rules.TestWatcher;
import org.junit.runner.Description;

import org.openqa.selenium.OutputType;
import org.openqa.selenium.TakesScreenshot;
import org.openqa.selenium.WebDriver;

public class ScreenshotRule extends TestWatcher {

    private WebDriver driver = null;
    public ScreenshotRule(WebDriver driver) {
        this.driver = driver;
    }

    @Override
    protected void failed(final Throwable e, final Description description) {

        String userDir = System.getProperty("user.dir");
        String baseDir = userDir + "/failed-screenshots/" 
                + description.getClassName() + "/";
        String screenshotName = description.getClassName() + "." 
                + description.getMethodName() + ".png";

        File screen = null;
        screen = ((TakesScreenshot) driver).getScreenshotAs(OutputType.FILE);

        try {
            File dir = new File(baseDir);
            if(!dir.exists()) FileUtils.forceMkdir(dir);
            File localFile = new File(baseDir + screenshotName);
            FileUtils.copyFile(screen, localFile);

            // Work with JUnit Attachments plugin to attach the files 
            // produced by Junit to Jenkins
            System.out.println("[[ATTACHMENT|" + baseDir + screenshotName + "]]");
        } catch (IOException ioe) {
            ioe.printStackTrace();
        }
    }
}

Working with JUnit attachment plugin, System.out.println("[[ATTACHMENT|" + baseDir + screenshotName + "]]"); will help Jenkins to collect the screenshot as JUnit attachment.